What to do with hydrangeas in September to keep your plants looking their best and bag some free plants next year too

Hydrangeas are at their peak from late spring through to autumn, but in September you'll find their blooms starting to peter out. There are several things you should do with hydrangeas in September as the blooms near their end to get them ready for next year.

Autumn hydrangea care is quite straightforward, involving protecting them with mulch ahead of winter and leaving the heads intact. However, in September there are a few other jobs you can do that will not only keep your plants looking their best but could give you some free plants for next year too.

Chris Bonnett founder of GardeningExpress says, 'September is a good time of year to give hydrangeas a little more attention. For example, spent flowerheads can be left alone over autumn and winter as they add a gorgeous look to the garden, especially when frost arrives.'

1. Don't hard prune

It's vital that you don't over-prune hydrangeas at this time of year. Richard Barker, horticultural expert and commercial director at LBS Horticulture explains why: 'Faded flowerheads should be left intact and on hydrangeas over winter. This is because they will naturally insulate the following year's flower buds from the cold winds and frosts in winter.'

'If you really don’t like the look of browned blooms, you can snip off just the flower head,' suggests Julian Palphramand, head of plants at British Garden Centres. 'Cut the stem just below the spent flower, but don’t take much off and avoid cutting into the thicker, woody stems. For lacecap varieties, you can cut the faded heads back after flowering to the second pair of leaves below the head to stop seed forming, which saps energy.'

When you are giving your hydrangeas a little prune it's also a great time to check for pests and diseases.

2. Take cuttings

September is the last possible time to take cuttings from your hydrangea before it goes into its winter dormancy. You can take semi-ripe ones, which is when the base of the stem is beginning to get woody, but the tip is still green.

'When taking cuttings from hydrangeas at this time of year, look for healthy, straight stems from this year's growth which are free of flowers or flower buds,' advises Lucie Bradley, gardening and greenhouse expert at Harvst Automatic Watering. 'You need to cut a length of approx 10 to 15cm in length, cutting through the stem just below a leaf node where there is a high concentration of plant cells and hormones which will trigger root growth.'

According to Lucie, the roots should start to appear after 4 to 6 weeks, and from that point onwards your new hydrangea has time to develop a healthy root system ready for next spring.

3. Keep watering

One thing that is important is to keep watering. 'We’ve had some rainfall so far, but if September is dry where you are, then continue to water newly planted hydrangeas and keep a close eye on those in containers,' suggests Chris.

Julian agrees, 'The phrase “water until the ground freezes” is useful: well-hydrated roots cope with winter far better than dry ones.'

You can check the soil's moisture levels with a tester – we like the XLUX long probe plant soil moisture meter, £12.99, Amazon, or have a good feel about the soil and see if it feels moist further down or not.

4. Use mulch

Mulching is such a key element for healthy plants and for locking in moisture – it's a must-have buy for every garden – or make your own! It also suppresses weeds and insulates your hydrangea from the cold months that lie ahead.

'Mulching around the base of hydrangeas will help to protect the plants from frosts and retain moisture,' says Richard. 'Use an organic material like bark, leaf mould or rotted manure, ensuring that the mulch does not actually touch the stem of the plant to prevent rotting.'

Amazon sell leaf mould compost, 50 litres by Happy Earth Soil for £18.98, it's made from 100% fallen leaves making it a living compost with worm castings and microbes.

5. Stop fertilising

'In September, you should stop feeding hydrangeas if you are still doing so,' advises Richard. 'Fertilising can encourage the plant to produce new, weak growth that can be easily damaged by autumn frosts.'

'If you feed at all,' adds Julian, 'Use a low‑nitrogen, high‑potash feed so you don’t push soft growth that winter will hit.'

We like Westland's sulphate of potash fertiliser, 1.5kg for £11.99, Amazon.

Your pruning kit essentials

Follow these top tips this September and your hydrangeas will survive the winter well.